1. Field of the Invention
The present invention relates to an encrypted data recording apparatus, and, more particularly to an encrypted data recording apparatus such as a network attached storage for recording encrypted content data for copyright protection and the like.
2. Description of the Related Art
In recent years, a digital AV system and the like that record digital contents such as digitized videos and sound in recording (storage) devices such as a hard disk device and reproduce the digital contents are becoming increasingly popular.
A network attached storage (NAS) is widely spread as a storage that can be easily connected from a personal computer connected to a network according to a method based on a so-called Ethernet (registered trademark) conforming to IEEE (Institute of Electrical and Electronics Engineers) 802.3 or a wireless standard conforming to IEEE 802.11.
For example, a recording apparatus of a mirroring type for backup of data may be used in a server on a network. FIG. 10 is a diagram showing a structure of a general mirroring-type network attached storage. In this mirroring-type network attached storage, a data recording apparatus 210, which is a network attached storage, is connected to a network 100 based on the Ethernet (registered trademark), a wireless LAN standard conforming to IEEE 802.11, or the like. The data recording apparatus 210 is connected to the network 100 via a network interface 211 and an MAC (Media Access Control) block 212. The MAC block 212 is connected to, for example, a PCI (Peripheral Component Interconnect) bus 213, which is an internal bus of the data recording apparatus 210. A CPU 214 serving as control means, a ROM 215 in which programs and the like are stored, and a RAM 216 serving as data storing means are connected to the PCI bus 213. Two recording means (data storages) 218a and 218b such as hard disks are connected to the PCI bus 213 via a bus bridge 217. For example, an EPROM (Erasable and Programmable Read Only Memory) is used as the ROM 215. For example, an SDRAM (Synchronous Dynamic Random Access Memory) is used as the RAM 216.
The data recording apparatus 210 performs writing and the like of files to record the same contents in the recording means 218a and 218b. In other words, in writing a file in the recording means 218a, the data recording apparatus 210 writes the file in the recording means 218b as well. In deleting a file, the data recording apparatus 210 deletes both the file in the recording means 218a and the file in the recording means 281b simultaneously (sequentially in terms of time). The data recording apparatus 210 may read out a file from any one of the hard disks.
In the case of such a mirroring-type network attached storage, there is an advantage that it is possible to normally continue an operation even if one of the hard disks is out of order. In other words, it can be said that one of the recording means functions as a backup. Therefore, if one of the recording means is out of order, it is possible to normally continue a mirroring operation by replacing the recording medium.
In the past, among apparatuses that communicate according to the Internet Protocol (IP), it was difficult to transmit and receive contents such as copyrighted video data. However, in 2004, an official standard was issued as a part of the DTCP (Digital Transmission Contents Protection) standard and license of such contents was started. This makes it possible to circulate copyrighted data using the DTCP/IP, for example, on the Ethernet (registered trademark). It is also possible to store copyrighted data such as contents permitted to be recorded and stored like so-called Copy Once (may be copied only once) (see, for example, JP-A-2004-194295).
As states of the copyrighted contents, there are about three states. Specifically, the states are “Copy Never”, i.e., a state in which it is not permitted to copy contents, “Copy Once”, i.e., a state in which it is permitted to copy contents only once, and “Copy No More”, i.e., a state in which it is not permitted to record contents of “Copy Once” and further copy the contents.
For example, in a DVD (Digital Versatile Disk) recorder and the like, “Copy Once” contents are usually stored in a hard disk under the present situation. However, it is difficult for a general user to keep a backup because of the characteristic that copying is not permitted. On the other hand, in a usual agreement with a copyright holder, it is permitted to back up contents. However, it is prohibited to allow another apparatus to reproduce the contents backed up. In other words, it is prohibited to multiply copies of the contents.